This invention relates to a photoconductive material for use in photosensitive drums of copiers and printers, photosensors, solar cells and thin film transistors. More specifically, this invention relates to a photoconductive structure comprising a carrier generating region of a wide band gap material scattered in an amorphous silicon material.
Conventionally, hydrogen or fluorine has been used in the amorphous silicon to reduce the state density that is formed in the forbidden band in the vicinity of the conduction band and the valence band by terminating the dangling bond of silicon. Such a termination of the dangling bond results in a high photosensitivity of the amorphous silicon devices and also enables the doping of the amorphous silicon to any of P- and N-types. The amorphous silicon thus obtained are used to develop various devices and attempts have been made to apply these materials to sensors, solar cells, photosensitive fields and other devices.
In recent years, there is a demand of photosensors that have a high sensitivity in the wavelength of visible optical radiation, particularly of the wavelength of blue lights. In consequence, there is an increasing need of the photoconductor having a high photosensitivity and simultaneously a wide band gap.
In many cases, the wide band gap material is formed by incorporating oxygen, nitrogen, carbon etc. into an amorphous silicon matrix. However, while the amorphous silicon photoconductor thus formed has the desirable wide band gap, there is a problem in that the mobility of carriers in the photoconductor tends to decrease due to the incorporated elements that also act as the trap of careers. Therefore, there is a disadvantage that the desired high photosensitivity of such a silicon photoconductor for the short wavelength optical radiation is harmfully reduced due to the decrease in the mobility of the carriers.